Originally Posted by nik
It was braked trailers I was puzzled about.
I suspect it's the critical mass that is the issue with braked trailers.
Unbraked up to 750kg or 50% of the tow car.
My car has a towing capacity of 2000kg vs a vehicle weight of 1660kg
I would not tow a trailer weighing above the car weight, imagine the tail wagging the dog!
When I had a Landcruser it weighed 2500kgs and was rated to tow 3500kgs.
Imagine that lot if the coupling detached (yet the trailer was still attached to the tow by a wire or chain) with the trailer brakes now inoperative because the over run brake mechanism depends on the hitch being coupled correctly.
The reason for a breakaway cable is to apply the trailer brakes ASAP following unintentional uncoupling, leaving the towing vehicle to it's own devices.
With an unbraked trailer the towing vehicle is the only means of any attempt to control stopping the trailer should it become unattached.
Hence the weight limit on unbraked trailers and the strong wire/chain to prevent runaway.
Just thinking about the possible scenarios is scary enough for me so I hope I am never subjected to such an event.